JP5467964B2 - Power conversion control device and power conversion control method - Google Patents

Description

The present invention relates to a power conversion control device and a power conversion control method, and more particularly to a power conversion control device and a power conversion control method that are suitable for use when performing power conversion using a switching element.

  Electric vehicles such as EVs (Electric Vehicles), HEVs (Hybrid Electric Vehicles), and PHEVs (Plug-in Hybrid Electric Vehicles) have two types of batteries: high-voltage batteries and low-voltage batteries. Is usually provided.

  The high-voltage battery is mainly used as a power source for high-voltage and high-power loads such as a main power motor for driving and driving wheels of an electric vehicle, and an A / C (air conditioner) compressor motor. . On the other hand, low-voltage batteries are low-voltage and low-power loads such as various ECUs (Electronic Control Units), EPS (electric power steering), electric brakes, car audio equipment, wipers, motors for power windows, lighting lamps, etc. Mainly used as a power source for

  The low voltage battery is charged by, for example, transforming and supplying the voltage of the high voltage battery with a DCDC converter.

  For a DCDC converter used in this type of electric vehicle, a semiconductor switching element made of, for example, an FET (Field Effect Transistor) is used. If the temperature of the semiconductor switching element rises due to poor cooling or the like, the semiconductor switching element may break down.

  Therefore, conventionally, the semiconductor switching element is driven by PWM (Pulse Width Modulation) control, the temperature of the semiconductor switching element or its surroundings is detected, and the duty ratio of the PWM control is adjusted according to the detected temperature, so that the semiconductor Control of overheating of the switching element is performed (for example, refer to Patent Documents 1 and 2).

  However, Patent Documents 1 and 2 do not discuss any countermeasures in the case where an abnormality occurs in the temperature sensor used for temperature detection and the temperature cannot be normally detected.

JP 2000-341801 A JP 2006-288047 A

  The present invention makes it possible to continue the operation even when the temperature of the power conversion means such as a DCDC converter cannot be normally detected.

A power conversion control device according to one aspect of the present invention is a power conversion control device that controls a power conversion unit that converts an input first voltage into a second voltage, and a temperature detection unit that detects a temperature of the power conversion unit. And current detection means for detecting at least one of an input current value or an output current value to the power conversion means, based on the temperature detected by the temperature detection means and the current value detected by the current detection means, Output control means for controlling the output voltage of the power conversion means, and the output control means uses the output power of the power conversion means when the temperature detected by the temperature detection means is outside a predetermined condition. when the charging rate of the battery being charged is equal to or greater than a predetermined threshold value, the output of the power conversion unit is stopped, when the charging rate of the battery is less than the threshold value, the output voltage After lowering to a constant voltage, when the charging rate of the battery becomes equal to or higher than the threshold, it stops the output of the power converter.

In the power conversion control device according to one aspect of the present invention, the temperature of the power conversion unit is detected, and at least one of the input current value or the output current value to the power conversion unit is detected, and the detected temperature and current value are determined. The output voltage of the power conversion means is controlled on the basis, and when the detected temperature is out of a predetermined condition, the output voltage is controlled without using the detected temperature, and the detected temperature is When the state deviating from the condition continues for a predetermined time, when the charging rate of the battery charged by the output power of the power conversion unit is equal to or greater than a predetermined threshold, the output of the power conversion unit is stopped and the battery When the charging rate of the battery is less than the threshold value, the output voltage is lowered to a predetermined voltage, and then when the charging rate of the battery becomes equal to or higher than the threshold value, the output of the power conversion means It is stopped.

Therefore, even when the temperature of the power conversion unit cannot be normally detected, the operation of the power conversion unit can be continued. In addition, when the temperature of the power conversion unit cannot be detected normally, the battery can be continuously charged within a range in which the failure of the power conversion unit does not occur, thereby preventing the battery capacity from being insufficient.

  This power conversion means is composed of, for example, a DCDC converter, a rectifier, an inverter, and the like. This temperature detection means is comprised by the temperature sensor using a thermistor, a thermocouple, a resistance temperature detector, etc., for example. This current detection means is constituted by a current sensor, for example. This output control means includes, for example, a microcomputer, various processors, a control circuit, and the like.

The output control means may stop the output of the power conversion means when the current detected by the current detection means exceeds a predetermined threshold after the output voltage is lowered to the predetermined voltage. it can.

  Thereby, when it becomes impossible to detect the temperature of the power conversion means normally, it is possible to more reliably prevent the power conversion means from failing while continuing to charge the battery.

The power conversion control method according to one aspect of the present invention is a power conversion control method for controlling a power conversion unit that converts an input first voltage into a second voltage, and a temperature detection step of detecting a temperature of the power conversion unit. And a current detection step for detecting at least one of an input current value or an output current value to the power conversion means, and the output voltage of the power conversion means is controlled and detected based on the detected temperature and current value. If the charged temperature deviates from a predetermined condition, and the charging rate of the battery charged by the output power of the power conversion means is equal to or higher than a predetermined threshold, the output of the power conversion means is stopped, and the battery When the charging rate is less than the threshold, after the output voltage is lowered to a predetermined voltage, when the charging rate of the battery becomes equal to or higher than the threshold, the output of the power conversion means is output. Characterized in that a and an output control step of stopping.

In the power conversion control method according to one aspect of the present invention, the temperature of the power conversion unit is detected, and at least one of an input current value or an output current value to the power conversion unit is detected, and the detected temperature and current value are determined. The output voltage of the power conversion means is controlled on the basis, and when the detected temperature is out of a predetermined condition, the output voltage is controlled without using the detected temperature, and the detected temperature is When the state deviating from the condition continues for a predetermined time, when the charging rate of the battery charged by the output power of the power conversion unit is equal to or greater than a predetermined threshold, the output of the power conversion unit is stopped and the battery When the charging rate of the battery is less than the threshold value, the output voltage is lowered to a predetermined voltage, and then when the charging rate of the battery becomes equal to or higher than the threshold value, the output of the power conversion means It is stopped.

Therefore, even when the temperature of the power conversion unit cannot be normally detected, the operation of the power conversion unit can be continued. In addition, when the temperature of the power conversion unit cannot be detected normally, the battery can be continuously charged within a range in which the failure of the power conversion unit does not occur, thereby preventing the battery capacity from being insufficient.

  This power conversion means is composed of, for example, a DCDC converter, a rectifier, an inverter, and the like. This temperature detection step is executed by, for example, a temperature sensor using a thermistor, a thermocouple, a resistance temperature detector, or the like. This current detection step is executed by, for example, a current sensor. This output control step is executed by, for example, a microcomputer, various processors, a control circuit, and the like.

  According to one aspect of the present invention, even when the temperature of the power conversion unit cannot be normally detected, the operation of the power conversion unit can be continued.

It is a block diagram which shows one Embodiment of the vehicle-mounted system to which this invention is applied. It is a circuit diagram which shows the structural example of a DCDC converter. It is a graph which shows an example of a structure of a temperature characteristic. It is a figure which shows an example of the waveform of the drive signal of FET. It is a block diagram which shows the structural example of the function of the control circuit of a DCDC converter. It is a flowchart for demonstrating the output control process of a DCDC converter. It is a flowchart for demonstrating the detail of a temperature sensor diagnostic process. It is a flowchart for demonstrating voltage drop addition output control. It is a flowchart for demonstrating temperature suppression output control. It is a block diagram which shows the structural example of a computer.

Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described. The description will be given in the following order.
1. Embodiment 2. FIG. Modified example

<1. Embodiment>
[Configuration example of in-vehicle system 1]
FIG. 1 is a block diagram showing an embodiment of an in-vehicle system to which the present invention is applied. The in-vehicle system 1 is a system provided in an electric vehicle such as EV, HEV, and PHEV. The in-vehicle system 1 includes a high voltage battery 11, a DCDC converter 12, high voltage loads 13-1 to 13-m, a low voltage battery 14, a power management ECU 15, and low voltage loads 16-1 to 16-n. The DCDC converter 12, the power management ECU 15, and the low-voltage loads 16-1 to 16-n are connected to each other via an in-vehicle LAN (Local Area Network), and transmit and receive various data by CAN (Controller Area Network) communication. Do.

  The high voltage battery 11 supplies DC power of a predetermined voltage to the DCDC converter 12 and the high voltage loads 13-1 to 13-m.

  The DCDC converter 12 converts the voltage of the DC power supplied from the high voltage battery 11 and supplies the converted DC power to the low voltage battery 14, the power management ECU 15, and the low voltage loads 16-1 to 16-n. .

  The high-voltage loads 13-1 to 13-m are high-voltage loads driven by the electric power of the high-voltage battery 11, and include, for example, a main power motor of an electric vehicle and a compressor motor of an air conditioner.

  Hereinafter, the high-voltage loads 13-1 to 13-m are simply referred to as the high-voltage loads 13 when it is not necessary to individually distinguish them.

  The low voltage battery 14 supplies DC power of a predetermined voltage to the power management ECU 15 and the low voltage loads 16-1 to 16-n.

  The power management ECU 15 is an ECU that controls the power supply of the electric vehicle. For example, the power management ECU 15 controls charging and discharging of the high voltage battery 11 and the low voltage battery 14, and monitors the states of the high voltage battery 11, the low voltage battery 14, and the low voltage loads 16-1 to 16-n. Further, for example, the power management ECU 15 supplies the DCDC converter 12 with information indicating the states of the high voltage battery 11, the low voltage battery 15, and the low voltage loads 16-1 to 16-n. The power management ECU 15 is driven by the output power of the DCDC converter 12 or the power of the low voltage battery 14.

  The low voltage loads 16-1 to 16-n are low voltage loads driven by the output power of the DCDC converter 12 or the power of the low voltage battery 14, for example, EPS (electric power steering), electric brake, car audio equipment, A wiper and an ECU that controls at least a part of the electric vehicle are included.

  Hereinafter, when it is not necessary to individually distinguish the low-voltage loads 16-1 to 16-n, they are simply referred to as a low-pressure load 16.

[Configuration Example of DCDC Converter 12]
FIG. 2 is a circuit diagram illustrating a configuration example of the DCDC converter 12. In FIG. 2, the high-voltage load 13 connected to the input side of the DCDC converter 12 and the power management ECU 15 and the low-voltage load 16 connected to the output side of the DCDC converter 12 are not shown.

  The DCDC converter 12 includes a transformer 21, a temperature sensor 22, a current sensor 23, and a control circuit 24.

  The transformer unit 21 is configured by a so-called full-bridge type DC voltage conversion circuit, and includes a filter 31, FETs 32 a to 32 d, a resonance coil 33, a transformer 34, diodes 35 a and 35 b, a coil 36, and a capacitor 37.

  The electric power supplied from the high voltage battery 11 is AC-converted by an inverter constituted by bridge-connected FETs 32a to 32d. The filter 31 plays a role of removing high frequency noise generated by switching of the inverter so as not to leak to the front stage of the DCDC converter 12.

  The electric power converted by the inverter is converted into a voltage by the transformer 34 and also converted into a direct current by a rectifier circuit including the transformer 34 and the diodes 35a and 35b. Then, the harmonic component is removed by the LC filter composed of the coil 36 and the capacitor 37, and the DC power whose voltage is converted is output.

  Hereinafter, when it is not necessary to distinguish the FETs 32a to 32d, they are simply referred to as FET 32.

  The temperature sensor 22 is provided for detecting the temperature of the transformer 21. More specifically, the temperature sensor 22 is provided, for example, in the vicinity of the FET 32 or a radiator for the FET 32 in order to protect the FET 32 from overheating. The temperature sensor 22 supplies a signal representing the detected temperature to the control circuit 24.

  For example, the temperature sensor 22 is configured by a temperature detection circuit using a thermistor, and the output voltage (hereinafter also referred to as a detection voltage) of the temperature sensor 22 changes as the resistance of the thermistor changes with temperature.

  FIG. 3 is a graph showing an example of output characteristics of the temperature sensor 22. In FIG. 3, the horizontal axis indicates the temperature, and the vertical axis indicates the detection voltage. In this example, the temperature sensor 22 exhibits a characteristic that the detection voltage decreases as the temperature increases. Further, the temperature sensor 22 operates properly within a range from −40 ° C. to 150 ° C. That is, the temperature sensor 22 can detect a temperature within a range from −40 ° C. to 150 ° C. almost accurately. The detection voltage at −40 ° C. is 4.5V, and the detection voltage at 150 ° C. is 0.5V. Therefore, the detection voltage range in which the temperature sensor 22 can be properly used is 0.5V to 4.5V.

  In the following description, it is assumed that the temperature sensor 22 has the output characteristics shown in FIG.

  The current sensor 23 is provided at the output section of the transformer section 21 in order to detect an overcurrent of the transformer section 21, detects the output current of the transformer section 21, and outputs a signal indicating the detected current value to the control circuit 24. To supply.

  The control circuit 24 detects the output voltage at the point A of the transformer 21 and supplies a drive signal to each FET 32 so as to bring the output voltage close to the target voltage, and performs PWM control of the inverter composed of the FET 32.

  FIG. 4 shows an example of the waveform of the drive signal supplied from the control circuit 24 to each FET 32. As shown in this figure, the DCDC converter 12 employs a phase shift method in which a voltage is applied to the transformer 34 by shifting the phase of the period during which the diagonally located FET 32 is turned on. In the DCDC converter 12, ZVS (zero volt switching) type soft switching is performed using the inductance of the resonance coil 33 in front of the transformer 34 and the output capacity of the FET 32.

  Here, hereinafter, the ratio of the ON periods of the drive signals of the FETs 32a and 32d or the ratio of the ON periods of the drive signals of the FETs 32b and 32c is referred to as a Duty ratio. For example, if the length of the ON period of the drive signal of the FET 32a is α and the length of the period in which the ON periods of the drive signals of the FET 32a and FET 32d overlap is β, the duty ratio = β / α × 100 (%). In the phase shift method, the ratio between the ON period and the OFF period of the drive signal of each FET 32 is fixed to a predetermined value (for example, 1: 1).

  The output voltage of the transformer 21 is determined by the input voltage, the duty ratio, and the winding ratio of the primary side and the secondary side of the transformer 34. Accordingly, the control circuit 24 controls the output voltage of the transformer 21 by controlling the duty ratio.

[Configuration Example of Function of Control Circuit 24]
FIG. 5 is a block diagram illustrating a configuration example of functions of the control circuit 24. The control circuit 24 is configured to include a diagnosis unit 61, an output voltage detection unit 62, and a drive unit 63. The drive unit 63 is configured to include a duty setting unit 71 and a drive signal output unit 72.

  The diagnosis unit 61 performs an operation diagnosis of the temperature sensor 22 based on the detection voltage of the temperature sensor 22 and notifies the diagnosis result to the duty setting unit 71 of the drive unit 63.

  The output voltage detector 62 detects the output voltage at point A of the transformer 21 and notifies the detection result to the duty setting unit 71 of the drive unit 63.

  The drive unit 63 includes a temperature of the transformer 21 detected by the temperature sensor 22, an output current of the transformer 21 detected by the current sensor 23, an output voltage of the transformer 21 detected by the output voltage detector 62, and a diagnostic unit. Based on the diagnosis result of the temperature sensor 22 by 61 and the state of the high voltage battery 11, the low voltage battery 14 and the low voltage load 16 notified from the power management ECU 15, the duty ratio of the drive signal supplied to each FET 32 is set, and the drive signal output To the unit 72.

  The drive signal output unit 72 supplies a drive signal having a duty ratio set by the duty setting unit 71 to each FET 32, and performs PWM control of the inverter formed of the FET 32.

[Output control processing]
Next, output control processing of the DCDC converter 12 executed by the control circuit 24 will be described with reference to the flowchart of FIG. This process is started when, for example, a switch of the electric system of the electric vehicle provided with the in-vehicle system 1 is turned on, and is ended when the switch is turned off.

  In step S1, the diagnosis unit 61 performs a temperature sensor diagnosis process.

[Details of temperature sensor diagnosis processing]
Here, details of the temperature sensor diagnosis processing will be described with reference to the flowchart of FIG.

  In step S <b> 31, the diagnosis unit 61 acquires the detection voltage of the temperature sensor 22. The diagnosis unit 61 acquires the detection voltage of the temperature sensor 22 every 100 ms, for example.

  In step S32, the diagnosis unit 61 determines whether or not the detection voltage of the temperature sensor 22 is greater than a predetermined threshold value Vt1. If it is determined that the detected voltage is equal to or lower than the threshold value Vt1, the process proceeds to step S33. The threshold value Vt1 is set to 4.5 V, which is the upper limit of the detection voltage range in which the temperature sensor 22 can be properly used.

  In step S33, the diagnosis unit 61 determines whether or not the detection voltage of the temperature sensor 22 is less than a predetermined threshold value Vt2. If it is determined that the detected voltage is equal to or higher than the threshold value Vt2, the process proceeds to step S34. The threshold value Vt2 is set to 0.5 V, which is the lower limit of the detection voltage range in which the temperature sensor 22 can be properly used.

  In step S34, the diagnosis unit 61 determines whether or not the absolute value of the difference between the detected voltages of the current and previous temperature sensors 22 is greater than or equal to a predetermined threshold value ΔVt. If it is determined that the absolute value of the difference between the detected voltage of the current temperature sensor 22 and the previous temperature sensor 22 is less than the predetermined threshold value ΔVt, the process proceeds to step S35.

  Since the change in resistance of the thermistor with respect to the change in temperature is relatively slow, the threshold value ΔVt is set to a voltage that is normally assumed not to change during 100 ms, for example, 2.0V.

  In step S35, the diagnosis unit 61 clears the internal counter value.

  In step S36, the diagnosis unit 61 determines that the temperature sensor 22 is normal because the detected voltage of the temperature sensor 22 is within an appropriate range and the amount of change in the detected voltage of the temperature sensor 22 is within an assumed range. judge. Then, the diagnosis unit 61 notifies the duty setting unit 71 that the temperature sensor 22 is normal. Thereafter, the temperature sensor diagnosis process ends.

  On the other hand, if it is determined in step S32 that the detected voltage of the temperature sensor 22 is larger than the threshold value Vt1, if it is determined in step S33 that the detected voltage of the temperature sensor 22 is smaller than the threshold value Vt2, or this time and the previous time If it is determined that the absolute value of the difference between the detection voltages of the temperature sensor 22 is greater than or equal to the threshold value ΔVt, the process proceeds to step S37. That is, when the detected voltage (that is, the detected temperature) deviates from a predetermined condition that the detected voltage of the temperature sensor 22 is within an appropriate range and the amount of change in the detected voltage is within the assumed range, in other words, If the detected voltage deviates from the normal characteristics of the temperature sensor 22, the process proceeds to step S37.

  In step S37, the diagnosis unit 61 determines whether or not the internal counter value is equal to or greater than a predetermined threshold value Nt. If it is determined that the counter value is less than the threshold value Nt, the process proceeds to step S38. That is, the duration of the state where the detected voltage of the temperature sensor 22 is out of the proper range and the duration of the state where the change amount of the detected voltage is out of the assumed range are both defined by the threshold value Nt of the counter value. If it is less than the time (hereinafter referred to as abnormality determination time), the process proceeds to step S38.

  Note that the abnormality determination time is changed by changing the value of the threshold value Nt between the case where the detection voltage of the temperature sensor 22 is out of the proper range and the case where the change amount of the detection voltage is out of the assumed range. Also good.

  In step S38, the diagnosis unit 61 increments an internal counter value.

  In step S39, the diagnosis unit 61 determines that the state of the temperature sensor 22 is indefinite. Note that the state of the temperature sensor 22 being indeterminate means that the determination whether the temperature sensor 22 is normal or abnormal is not fixed. Then, the diagnosis unit 61 notifies the duty setting unit 71 that the state of the temperature sensor 22 is indefinite. Thereafter, the temperature sensor diagnosis process ends.

  On the other hand, if it is determined in step S37 that the counter value is equal to or greater than the threshold value Nt, the process proceeds to step S40. That is, when at least one of the duration of the state in which the detection voltage of the temperature sensor 22 is out of the appropriate range and the duration of the state in which the amount of change in the detection voltage is out of the assumed range is equal to or greater than the abnormality determination time The process proceeds to step S40.

  In step S40, the diagnosis unit 61 determines that the temperature sensor 22 is abnormal. Then, the diagnosis unit 61 notifies the duty setting unit 71 that the temperature sensor 22 is abnormal. Thereafter, the temperature sensor diagnosis process ends.

[Continuation of output control processing]
Returning to FIG. 6, in step S <b> 2, the duty setting unit 71 determines whether or not the temperature sensor 22 is abnormal based on the diagnosis result of the temperature sensor 22 by the diagnosis unit 61. If it is determined that the temperature sensor 22 is not abnormal, the process proceeds to step S3.

  In step S <b> 3, the duty setting unit 71 determines whether the state of the temperature sensor 22 is indefinite based on the diagnosis result of the temperature sensor 22 by the diagnosis unit 61. If it is determined that the state of the temperature sensor 22 is not indeterminate, that is, if it is determined that the temperature sensor 22 is normal, the process proceeds to step S4.

  In step S4, the duty setting unit 71 determines whether or not the temperature detected by the temperature sensor 22 is equal to or higher than a predetermined threshold value Tt1. Specifically, the duty setting unit 71 converts the detection voltage supplied from the temperature sensor 22 into a temperature based on predetermined data or a mathematical expression. If the duty setting unit 71 determines that the temperature detected by the temperature sensor 22 is less than the threshold value Tt1, the process proceeds to step S5.

  The threshold value Tt1 is set to a temperature slightly lower than the maximum allowable temperature, which is the maximum temperature at which the FET 32 can operate without failure. For example, when the maximum allowable temperature is 130 ° C., the threshold value Tt1 is set to 100 ° C.

  On the other hand, if it is determined in step S3 that the state of the temperature sensor 22 is indefinite, the process of step S4 is skipped, and the process proceeds to step S5.

  In step S5, the duty setting unit 71 determines whether or not the output current is greater than or equal to a predetermined threshold value It. Specifically, the duty setting unit 71 detects the output current of the transformer 21 based on the signal supplied from the current sensor 23 and compares it with the threshold value It. If the duty setting unit 71 determines that the output current is less than the threshold value It, the process proceeds to step S6.

  The threshold value It is set to a value of the output current at which the influence of the voltage drop due to the wiring resistance between the DCDC converter 12 and the low voltage battery 14 is at a level that cannot be ignored. For example, the threshold value It is set to 30A.

  In step S6, the drive unit 63 performs normal control. That is, the drive unit 63 drives the FET 32 without considering the temperature detected by the temperature sensor 22 and controls the output voltage of the transformer unit 21. For this normal control, for example, various known control methods can be employed.

  For example, the drive unit 63 controls the duty ratio of the drive signal of the FET 32 so that the output voltage of the transformer unit 21 is maintained at a predetermined voltage (for example, 12 V). Alternatively, for example, the drive unit 63 controls the duty ratio of the drive signal of the FET 32 so that the change in the output voltage of the transformer unit 21 is within a predetermined range regardless of the temperature detected by the temperature sensor 22. Alternatively, for example, the drive unit 63 controls at least one of the output voltage or the output current of the transformer unit 21 according to the load state of the DCDC converter 12.

  At this time, for example, the drive unit 63 performs feedback control so that the command value of the output voltage is equal to the actual output voltage of the transformer 21. For example, when the drive unit 63 is configured by a processor such as a CPU (Central Processing Unit), PID (Proportional Integral Differential) control is performed. Specifically, the duty setting unit 71 calculates the duty ratio by the following equation (1), which is a general equation for PID control.

Duty ratio = Gp x (V-V command) + Gd x d (V-V command) + Gi x ∫ (V-V command) dt
... (1)

  Gp, Gd, and Gi are constants, V is a detected value of the output voltage of the transformer 21, and V command is a command value of the output voltage of the transformer 21 (target value of the output voltage). Therefore, the V-V command is a deviation (error) between the target value of the output voltage and the actual output voltage.

  The drive signal output unit 72 controls the output voltage of the transformer unit 21 by setting the duty ratio of the drive signal supplied to each FET 32 to the value calculated by the equation (1).

  Further, for example, the drive unit 63 may be configured by an electronic component such as an operational amplifier, and feedback control of the output voltage of the transformer unit 21 may be performed by a known method.

  As described above, when the detected temperature is less than the threshold value Tt1 and the output current is less than the threshold value It, there is little possibility of overheating failure of the FET 32, and the voltage drop due to the wiring resistance is small. Without this, normal control for maintaining the output voltage at the target voltage is performed.

  If it is determined that the state of the temperature sensor 22 is indeterminate and the output current is less than the threshold It, the detected temperature is low in reliability and the voltage drop due to the wiring resistance is small. In addition, normal control for maintaining the output voltage at the target voltage is performed without considering the voltage drop.

  Thereafter, the process returns to step S1, and the processes after step S1 are executed.

  On the other hand, if it is determined in step S5 that the output current is equal to or greater than the predetermined threshold It, the process proceeds to step S7.

  In step S7, the drive unit 63 performs voltage drop addition output control. Thereafter, the process returns to step S1, and the processes after step S1 are executed.

[Voltage drop addition output control]
Here, the details of the voltage drop addition output control will be described with reference to the flowchart of FIG.

  If the output voltage exceeds the threshold It, the output voltage may fall below a predetermined allowable range due to a voltage drop due to wiring resistance. Therefore, the drive unit 63 corrects the duty ratio so as to cancel the influence of the wiring resistance.

  Specifically, in step S61, the duty setting unit 71 calculates a correction amount for the duty ratio by the following equation (2).

  Correction amount = a × (I × R (1 + b × T)) (2)

  Here, I represents the output current, R represents the wiring resistance, and T represents the detected temperature. Further, a and b are coefficients having predetermined values.

  The wiring resistance is caused by, for example, the resistance of the electric wire, the circuit resistance, the resistance of the connection portion of the terminal or the connector, and the wiring resistance R of Expression (2) is obtained in advance by actual measurement or calculation. However, since the wiring resistance is mainly made of metal (for example, copper), the resistance value increases with temperature. Therefore, in Equation (2), the temperature of the wiring resistance R is corrected by multiplying the wiring resistance R by (1 + b × T). Therefore, I × R (1 + b × T) in the equation (2) represents a voltage drop amount due to the wiring resistance subjected to temperature correction.

  Further, since the duty ratio of the drive signal of the FET 32 and the output voltage of the transformer 21 are in a proportional relationship, the duty ratio may be increased in order to compensate for the voltage drop due to the wiring resistance. The coefficient a in Expression (2) is a positive value coefficient and is a coefficient for determining the degree of compensation for the voltage drop due to the wiring resistance.

  The coefficients a and b are obtained by experiment, for example.

  Here, an example of a method for setting the coefficients a and b will be briefly described.

  For example, assuming that the wiring resistance is generated only by the harness, and the harness size is 8 sq and 5 m, the harness resistance R20 at 20 ° C and the harness resistance R0 at 0 ° C are expressed by the following equations (3), (4 ).

R20 = ρ × L / S = 1.68 × 10 ^-10 × 5m / 8mm ² ≒ 1.31mΩ (3)
R0 = R20 × (1 + α20 (0 ℃ -20 ℃))
= 1.31 × (1 + 0.00393 × -20)) ≒ 1.21mΩ (4)

  Here, ρ represents the volume resistivity of copper, and α represents a conductor temperature resistance coefficient (α20 is a coefficient at 20 ° C.).

  Since the resistance of the harness can be expressed by a linear function with temperature as a variable, the resistance R of the harness when the temperature is T ° C. is obtained by the following equation (5).

  R = R0 × (1 + α0 (T ℃ −0 ℃)) = R0 × (1 + 0.004265 × T) (5)

  Therefore, the constant b in Equation (2) is 0.004265.

  In this case, the voltage drop amount ΔV = RI = 0.131 × 60 = 0.79V due to the harness when the output current is 60 A and the temperature is 20 ° C. Therefore, at this time, the duty ratio may be corrected so that the output voltage increases by 0.79V.

  For example, if the input voltage of the transformer 21 is 334V and the winding ratio of the transformer 34 is 8: 1, the duty ratio is increased by 0.79 / (334/8) × 100% = 1.9% to increase the output voltage by 0.79V. Increase it. Therefore, if the correction amount = 1.9%, I = 60 A, R (1 + b × T) = 1.31 mΩ is substituted into the equation (2), the value of the coefficient a is 2.4. However, the value of the coefficient a varies depending on the input voltage.

  Returning to FIG. 8, in step S62, the duty setting unit 71 corrects the duty ratio by adding the correction amount obtained in step S61 to the current duty ratio. The duty setting unit 71 outputs the corrected duty ratio to the drive signal output unit 72. The drive signal output unit 72 changes the duty ratio of the drive signal supplied to each FET 32 to a corrected value. Thereafter, the voltage drop addition output control ends.

[Continuation of output control processing]
Returning to FIG. 6, when it is determined in step S4 that the temperature is equal to or higher than the threshold value Tt1, the process proceeds to step S8.

  In step S8, the drive unit 63 performs temperature suppression output control.

[Details of temperature suppression output control]
Here, the details of the temperature suppression output control will be described with reference to the flowchart of FIG.

  When the temperature is equal to or higher than the threshold value Tt1, if the temperature rise continues as it is, the FET 32 may overheat and break down. Therefore, the duty ratio is corrected so as to suppress the heat generation of the FET 32 by the temperature suppression output control.

  In step S81, the duty setting unit 71 calculates a correction amount for the duty ratio by the following equation (6).

  Correction amount = c × (T−Tt1) (6)

  Here, T represents the detected temperature, and c is a coefficient of a predetermined value. The coefficient c is determined by experiments and the like. For example, when the temperature is 130 ° C. and the duty ratio is decreased by 6%, the coefficient c = 0.2.

  In step S <b> 82, the duty setting unit 71 determines whether or not there is a drive request for the low-voltage load 16 based on information from the power management ECU 15. If it is determined that there is no request for driving the low-pressure load 16, the process proceeds to step S83.

  In step S83, the duty setting unit 71 corrects the duty ratio to a value obtained by subtracting the correction amount obtained in step S82 from the current duty ratio. The duty setting unit 71 outputs the corrected duty ratio to the drive signal output unit 72. The drive signal output unit 72 changes the duty ratio of the drive signal supplied to each FET 32 to a value after correction.

  As the difference between the detected temperature and the threshold value Tt1 increases according to the equation (6) described above, the correction amount increases and the duty ratio decreases. Accordingly, the output current is reduced, the loss generated in the FET 32, the transformer 34, the diodes 35a and 35b, and the wiring is reduced, the heat generation is suppressed, the temperature rise of the FET 32 and the surroundings is suppressed, and the FET 32 is prevented from overheating. The

  Thereafter, the temperature suppression output control ends.

  On the other hand, if it is determined in step S82 that there is a drive request for the low-pressure load 16, the process proceeds to step S84.

  In step S84, the duty setting unit 71 determines whether or not the drive request for the low-pressure load 16 continues for a predetermined time. If it is determined that the drive request for the low-pressure load 16 has not continued for a predetermined time, the process proceeds to step S85.

  In step S85, the duty setting unit 71 determines whether or not the detected temperature is equal to or higher than a predetermined threshold value Tt2. If it is determined that the detected temperature is less than the threshold value Tt2, the process proceeds to step S86.

  The threshold value Tt2 is set to the maximum allowable temperature of the FET 32 described above, for example. For example, when the maximum allowable temperature of the FET 32 is 130 ° C., the threshold value Tt2 is set to 130 ° C.

  In step S86, the duty setting unit 71 corrects the duty ratio to a value obtained by subtracting the correction amount obtained in step S82 from the current duty ratio and further adding the load. Here, the load addition is a correction amount that is set according to the load amount of the low-voltage load 16 that is requested to be driven. The duty setting unit 71 outputs the corrected duty ratio to the drive signal output unit 72. The drive signal output unit 72 sets the duty ratio of the drive signal supplied to each FET 32 to a value after correction.

  As a result, the low voltage load 16 can be operated normally as much as possible within a range in which the overheating failure of the FET 32 does not occur.

  Thereafter, the temperature suppression output control ends.

  On the other hand, when it is determined in step S85 that the temperature detected by the temperature sensor 22 is equal to or higher than the threshold value Tt2, the process proceeds to step S83, and the process of step S83 described above is executed to reduce the load amount of the low-pressure load 16. The duty ratio is corrected without consideration. That is, when the temperature is equal to or higher than the threshold value Tt2, if the temperature rise is not immediately suppressed, there is a high possibility that an overheating failure of the FET 32 will occur. Priority is given to lowering the temperature. Thereafter, the temperature suppression output process ends.

  If it is determined in step S84 that the drive request for the low-pressure load 16 continues for a predetermined time, the process proceeds to step S83, and the process of step S83 described above is performed. That is, after a predetermined time has elapsed since the start of the drive request for the low-voltage load 16, it is unlikely that a temporary overcurrent such as an inrush current will occur. Therefore, lowering the output voltage and lowering the temperature have priority. Executed. Thereafter, the temperature suppression output process ends.

[Continuation of output control processing]
Returning to FIG. 6, when it is determined in step S2 that the temperature sensor 22 is abnormal, the process proceeds to step S9.

  In step S <b> 9, the duty setting unit 71 determines whether or not the SOC (State of Charge, charging rate) of the low voltage battery 14 is equal to or greater than a predetermined threshold value St, based on information from the power management ECU 15. When it is determined that the SOC of the low voltage battery 14 is less than the threshold value St, the process proceeds to step S10.

  In step S10, the drive unit 63 sets the duty ratio to the minimum voltage duty ratio. Here, the minimum voltage duty ratio is a duty ratio necessary for outputting the minimum voltage necessary for charging the low voltage battery 14 from the DCDC converter 12. The minimum voltage Duty ratio varies depending on the input voltage to the transformer 21, that is, the voltage of the high voltage battery 11. For example, when the minimum voltage required for charging the low voltage battery 14 is 9V, the minimum voltage duty ratio when the input voltage is 220V is about 60%, and the minimum voltage duty ratio when the input voltage is 334V is about 42%. %, The minimum voltage duty ratio when the input voltage is 400V is about 37%.

  The duty setting unit 71 outputs the minimum voltage duty ratio to the drive signal output unit 72. The drive signal output unit 72 changes the duty ratio of the drive signal supplied to each FET 32 to the minimum voltage duty ratio. Thereby, the output voltage of the transformer 21 is lowered to the minimum voltage necessary for charging the low voltage battery 14.

  In step S11, as in the process of step S5, it is determined whether or not the output current is greater than or equal to the threshold value It. If it is determined that the output current is less than the threshold value It, the process returns to step S9. Thereafter, the processes in steps S9 to S11 are repeatedly executed until it is determined in step S9 that the SOC of the low voltage battery 14 is equal to or greater than the threshold value St, or in step S11, it is determined that the output current is equal to or greater than the threshold value It. Is done. As a result, even when the temperature sensor 22 is abnormal, charging of the low voltage battery 14 is continued while suppressing an increase in temperature, and the low voltage load 16 is prevented from becoming inoperable due to insufficient capacity of the low voltage battery 14.

  On the other hand, if it is determined in step S9 that the SOC of the low voltage battery 14 is equal to or greater than the threshold value St, or if it is determined in step S11 that the output current is equal to or greater than the threshold value It, the process proceeds to step S12.

  In step S12, the DCDC converter 12 stops the output. Specifically, the duty setting unit 71 instructs the drive signal output unit 72 to stop outputting the drive signal, and the drive signal output unit 72 stops supplying the drive signal to the FET 32. Thereby, the output of the DCDC converter 12 is stopped.

  That is, when the temperature sensor 22 is abnormal, it is not possible to detect overheating of the FET 32. Therefore, when the output current exceeds the threshold value It, the output of the DCDC converter 12 is stopped. Thereby, for example, it is prevented that an overcurrent flows through the transformer 21 due to an abnormality such as a short circuit failure and an overheat failure of the FET 32 occurs.

  Further, when the temperature sensor 22 is abnormal, when the SOC of the low voltage battery 14 is equal to or higher than the threshold value St, or when the SOC is equal to or higher than the threshold value St, the low voltage load 16 may not operate due to insufficient capacity of the low voltage battery 14. Is low, the output of the DCDC converter 12 is stopped.

  Thereafter, the output control process ends.

  As described above, it is possible to prevent an abnormality from occurring in the DCDC converter 12 due to an overheating failure of the FET 32 without detecting a temperature abnormality due to an abnormality in the temperature sensor 22.

  Further, even if an abnormality occurs in the temperature sensor 22 and the temperature cannot be normally detected, the DCDC converter 12 can be appropriately operated within a range where the abnormality does not occur, and the low-voltage load 16 is stabilized. It can be operated.

<2. Modification>
In the above description, an example in which the duty ratio is controlled using the output current has been described. However, the current sensor 23 is provided in the input section of the transformer 21, the input current is detected, and the duty ratio is controlled using the input current. May be performed.

  Further, a shunt resistor may be provided instead of the current sensor 23, and the current may be obtained indirectly by measuring the voltage across the shunt resistor.

  Furthermore, in the above description, the example in which the present invention is applied to the DCDC converter 12 for an electric vehicle has been described. However, the present invention can be applied to a DCDC converter for other purposes.

  In addition to the DCDC converter, the present invention can also be applied to a power conversion device using a switching element, such as a rectifier and an inverter.

  The series of processes described above can be executed by hardware or can be executed by software. When a series of processing is executed by software, a program constituting the software is installed in the computer. Here, the computer includes, for example, a general-purpose personal computer capable of executing various functions by installing various programs by installing a computer incorporated in dedicated hardware.

  FIG. 10 is a block diagram illustrating an example of a hardware configuration of a computer that executes the above-described series of processing by a program.

  In a computer, a central processing unit (CPU) 201, a read only memory (ROM) 202, and a random access memory (RAM) 203 are connected to each other by a bus 204.

  An input / output interface 205 is further connected to the bus 204. An input unit 206, an output unit 207, a storage unit 208, a communication unit 209, and a drive 210 are connected to the input / output interface 205.

  The input unit 206 includes a keyboard, a mouse, a microphone, and the like. The output unit 207 includes a display, a speaker, and the like. The storage unit 208 includes a hard disk, a nonvolatile memory, and the like. The communication unit 209 includes a network interface and the like. The drive 210 drives a removable medium 211 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory.

  In the computer configured as described above, the CPU 201 loads, for example, the program stored in the storage unit 208 to the RAM 203 via the input / output interface 205 and the bus 204 and executes the program. Is performed.

  The program executed by the computer (CPU 201) can be provided by being recorded on the removable medium 211 as a package medium or the like, for example. The program can be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

  In the computer, the program can be installed in the storage unit 208 via the input / output interface 205 by attaching the removable medium 211 to the drive 210. The program can be received by the communication unit 209 via a wired or wireless transmission medium and installed in the storage unit 208. In addition, the program can be installed in the ROM 202 or the storage unit 208 in advance.

  The program executed by the computer may be a program that is processed in time series in the order described in this specification, or in parallel or at a necessary timing such as when a call is made. It may be a program for processing.

  Further, in this specification, the system represents the entire apparatus constituted by a plurality of apparatuses.

  Furthermore, the embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

1 On-vehicle system 11 High voltage battery 12 DCDC converter 14 Low voltage battery 15 Power management ECU
16 Low voltage load 21 Transformer 22 Temperature sensor 23 Current sensor 24 Control circuit 32a to 32d FET
61 Diagnosis unit 62 Output voltage detection unit 63 Drive unit 71 Duty setting unit 72 Drive signal output unit

Claims (3)

In the power conversion control device for controlling the power conversion means for converting the input first voltage into the second voltage,
Temperature detection means for detecting the temperature of the power conversion means;
Current detection means for detecting at least one of an input current value or an output current value to the power conversion means;
Output control means for controlling the output voltage of the power conversion means based on the temperature detected by the temperature detection means and the current value detected by the current detection means, and
The output control means controls the output voltage without using the detected temperature when the temperature detected by the temperature detection means is out of a predetermined condition, and the temperature detected by the temperature detection means When the state deviating from the condition continues for a predetermined time, and when the charging rate of the battery charged by the output power of the power conversion unit is equal to or greater than a predetermined threshold, the output of the power conversion unit is stopped, and the battery When the charging rate of the battery is less than the threshold, the output voltage is lowered to a predetermined voltage, and then the output of the power conversion means is stopped when the charging rate of the battery exceeds the threshold. Power conversion control device. The output control means, after lowering the output voltage to the predetermined voltage, stops the output of the power conversion means when the current detected by the current detection means exceeds a predetermined threshold. The power conversion control device according to claim 1 . In a power conversion control method for controlling power conversion means for converting an input first voltage into a second voltage,
A temperature detection step of detecting the temperature of the power conversion means;
A current detection step of detecting at least one of an input current value or an output current value to the power conversion means;
Based on the detected temperature and current value, the output voltage of the power conversion means is controlled, and when the detected temperature is outside a predetermined condition, the output voltage is controlled without using the detected temperature. When the state where the detected temperature deviates from the condition continues for a predetermined time, and the charging rate of the battery charged by the output power of the power conversion unit is equal to or higher than a predetermined threshold, the power conversion unit The output is stopped, and when the battery charge rate is less than the threshold, the output voltage is lowered to a predetermined voltage, and then the output of the power conversion means when the battery charge rate is equal to or higher than the threshold. An output control step for stopping the power conversion control method.

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